[Q3] Quick-Check: ELECTROSTATICS

During a physics lab, a plastic strip was rubbed with cotton and became positively charged. The correct explanation for why the plastic strip becomes positively charged is that ...

• the plastic strip acquired extra protons from the cotton.
  
• the plastic strip acquired extra protons from the charging process 
• protons were created as the result of the charging process
  
• the plastic strip lost electrons to the cotton during the charging process 

 A balloon is rubbed against a student's hair and then touched to a wall. The balloon sticks to the wall due to

• magnetic forces between the particles of the balloon and the particles of the wall
• electrostatic forces between the particles of the balloon and the particles of the wall
• magnetic forces between the particles of the wall
• electrostatic forces between the particles of the balloon

A negatively charged plastic comb is brought close to, but does not touch, a small piece of paper. If the comb and the paper are attracted to each other, the charge on the paper

• must be positive
• must be negative
• may be neutral or negative
• may be neutral or positive 

Two electrically charged identical-sized metal spheres, A (charge of -4) and B (charge of +8). If the spheres are brought into contact, which sphere will have a net gain of electrons?

• both A and B
• neither
• only A
• only B

Two electrically neutral metal spheres, A and B, on insulating stands are placed in contact with each other. A negatively charged rod is brought near, but does not touch the spheres, as shown in the diagram below. How are the spheres now charged?

• A is positive and B is positive.
• A is negative and B is positive.
• A is positive and B is negative.
• A is negative and B is negative.

An electrostatic force of magnitude F exists between two metal spheres having identical charge q. The distance between their centers is r. Which combination of changes would produce no change in the electrostatic force between the spheres?

• doubling q on both spheres while halving r
• doubling q on one sphere while halving r
• doubling q on one sphere while doubling r
• doubling q on both spheres while doubling r

Which graph best represents the relationship between the magnitude of the electrostatic force and the distance between two oppositely charged particles?

• 
• 
• 
• 

The magnitude of the electrostatic force between two point charges is F. If the distance between the charges is doubled, the electrostatic force between the charges will become

• 4F

• 2F

In the diagram above, a positive test charge is located between two charged spheres, A and B. Sphere A has a charge of +2q and is located 0.2 meter from the test charge. Sphere B has a charge of -2q and is located 0.1 meter from the test charge. If the magnitude of the force on the test charge due to sphere A is F, what is the magnitude of the force on the test charge due to

sphere B?

Two positively charged masses are separated by a distance, r. Which statement best describes the gravitational and electrostatic forces between the two masses?

• The gravitational force is attractive and the electrostatic force is

  repulsive.

• The gravitational force is repulsive and the electrostatic force is

  attractive.

• Both forces are attractive.

• Both forces are repulsive.